Research on repetitive genetic elements of mammals was continued with emphasis on human Alu elements and other small RNA-encoding sequences. Alu sequences are small transposed elements endogenous to the human genome. Nearly one million dispersed copies constitute about 5% of our genetic material. Alu mobility causes genetic variability and heritable disorders. The regulated expression of Alu and its mouse homologue B1 into small RNA was studied. Germline and fetal-specific expression suggests their involvement in development. Examination of mechanisms of B1 and Alu RNA expression continued to yield insight into their complex regulation and propensity for transposition. Advances in understanding regulation of efficiency of transcription by RNA polymerase III were made. 1) A transcription termination and reinitiation factor for RNA polymerase III, previously identified as the human autoantigen La, was further characterized. 2) Human cDNAs for RNA binding proteins that modulate Alu RNA metabolism were isolated and characterized. 3) The gene encoding a trinucleotide repeat-containing Alu RNA binding protein was mapped to human chromosome l5q22. 4) The gene for all small cytoplasmic Y4 RNA gene was cloned, mapped to human chromosome 6 and its promoter elements functionally characterized.